Measuring Chemical Toxicity

August 15, 2005

One positive message in the latest federal report on toxic chemicals found in humans is that efforts to reduce exposure have proved effective.

Researchers have long warned about health threats from lead, secondhand smoke and certain once-popular pesticides. Recently, the Centers for Disease Control and Prevention reported that the level of harmful chemicals in blood and urine in those categories has dropped, sometimes substantially. Lead, for example, can damage children's brains. After it was removed from gasoline and paint, measurements showed steep declines in problematic levels in children. Close to 90 percent of children tested in the late 1970s had elevated levels of lead, compared with 1.6 percent in the latest study. CDC Director Julie L. Gerberding rightly hailed the outcome as an ``astonishing public health achievement.''

But not all the news was sanguine. The study recorded worrisome levels of cadmium in 5 percent of adults. Cigarette smoking is considered a likely source of the metal, which has been linked to kidney damage.

Researchers also measured potentially toxic levels of chemicals found in plastics, vinyl, insecticides and fragrances. Finally, the report said that more than 5 percent of women of childbearing age had mercury close to the level that could damage a fetus.

Scientists do not know the safe level for many chemicals that enter the body. Ill health effects can take decades to manifest.

That's why the CDC's tracking effort, which began four years ago, is so important. The latest report tested for 148 chemicals. The agency plans to expand that list in the future. That makes sense.

Some 80,000 chemicals are in use today and at least another 1,000 are added each year. As one scientist remarked, ``We live in a chemical world.''

Chemicals have many life-improving uses. Because of uncertainty about their potential side effects, however, continuing research is essential.